© 1998 by European Society of Cardiology
Copyright © 1998, European Society of Cardiology
Permissive effect of nitric oxide in arachidonic acid induced dilation in isolated rat arterioles
Laboratory for Physiology, Institute for Cardiovascular Research (ICaR-VU), Vrije Universiteit, Van der Boechorststraat 7, 1081 BT Amsterdam, Netherlands
* Corresponding author. Tel.: +31 (20) 444-8113; Fax: +31 (20) 444-8255.
Received 5 November 1997; accepted 3 February 1998
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Abstract |
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 Top Abstract 1 Introduction2 Methods3 Results4 DiscussionReferences |
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Objective: Prostaglandins and nitric oxide play an important role in the regulation of arteriolar tone. L-Arginine analogues inhibit nitric oxide formation, but may also inhibit arachidonic-acid induced dilation. Nitric oxide was found to stimulate cyclooxygenase activity in cultured endothelial cells. Therefore, we hypothesized that the non-specific inhibition of prostaglandin-related dilation by L-arginine analogues is a consequence of the absence of nitric oxide. Methods: To test this hypothesis, arteriolar segments from rat cremaster muscle were studied in a pressure myograph at 75 mmHg. Segments developed spontaneous tone, the diameter reduced from 179±3 to 98±3 µm (n=41). In this condition, responses to exogenous arachidonic acid (1 µM) were recorded and compared with responses after addition of L-NNA, and addition of either SNAP, nitroprusside or 8-Br-cGMP in the presence of L-NNA. Results: Inhibition of basal nitric oxide production with L-NNA (0.1 mM) reduced arachidonic acid-induced dilation (from 52±9 to 31±6 µm). In the presence of L-NNA, responses to arachidonic acid were augmented when exogenous nitric oxide was also present (SNAP, 31±6 µm vs. 75±5 µm; nitroprusside, 31±8 µm vs. 42±7 µm). Responses were not augmented with the second messenger of nitric oxide-mediated dilation 8-Br-cGMP (37±9 µm vs. 32±9 µm). Conclusions: These results indicate that nitric oxide directly increases arachidonic acid-induced dilation. Thus, the non-specific effect of L-arginine analogues can be explained by a permissive effect of nitric oxide on endothelial arachidonic acid metabolism.
KEYWORDS Artery; Endothelial factor; Nitric oxide; Prostaglandin; Vasoconstriction; Vasodilation
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1 Introduction |
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TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
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Arachidonic acid-derived metabolites play an important role in the regulation of vascular tone. Stimulation of vascular endothelial cells with agonists like bradykinin or acetylcholine often triggers the release of prostanoids (prostaglandins, prostacyclin and thromboxane) besides nitric oxide. The release of endogenous arachidonic acid from membrane fatty acids is catalyzed by phospholipase A2. Arachidonic acid is then converted to prostaglandin H2 by cyclooxygenase [1]. Two isozymes of cyclooxygenase exist, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), of which the latter is up regulated in inflammation. Dilatory prostanoids, prostacyclin and prostaglandin E2, are the most abundant prostanoids synthesized by the endothelium [1]. However, under pathophysiological conditions, the release of the vasoconstrictor prostaglandin H2 may be enhanced [2–5].
In isolated skeletal muscle arterioles, prostaglandins were found to mediate flow-induced dilation [6]and hypoxia-induced dilation [7]. In the same preparation, exogenous arachidonic acid induces a dilatory response that is abolished by the cyclooxygenase inhibitor indomethacin or by endothelium removal. Thus, exogenous arachidonic acid can be converted by the endothelium into dilatory prostaglandins. Surprisingly, the dilatory response to exogenous arachidonic acid was inhibited by L-arginine analogues in isolated rat arterioles and bovine arteries [8, 9]. L-Arginine analogues are tools to inhibit nitric oxide synthesis. Thus, it was concluded that L-arginine inhibitors have non-specific effects on other dilatory mechanisms. In vitro studies on cultured endothelial cells suggest that nitric oxide may stimulate the synthesis of prostaglandins in a cGMP-independent manner [10–12]. Therefore, we hypothesized that the ‘non-specific’ effect of L-arginine analogues on arachidonic acid induced dilation is the result of lowering the concentration of nitric oxide. We tested this hypothesis in isolated arterioles from rat cremaster muscle. The response to exogenous arachidonic acid was recorded in the presence and absence of the L-arginine analogue NG-nitro-L-arginine (L-NNA). In the presence of L-NNA, the effect of exogenous nitric oxide and 8-Br-cGMP was studied on the response to arachidonic acid. The nitric oxide donors SNAP and nitroprusside were used to compensate the inhibition of basal nitric oxide. The compound 8-Br-cGMP was used to discriminate between a direct effect of nitric oxide and secondary effects. We conclude that the inhibitory effect of L-NNA on arachidonic acid mediated dilation is probably the result of a permissive effect of nitric oxide on endothelial prostaglandin synthesis.
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2 Methods |
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2.1 Preparation and setup
The investigation conforms with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication No. 85-23, revised 1985). Procedures were approved by the local ethics committee for animal experimentation. Male Wistar rats of 281±5 g (n=33) were anaesthetized with sodium pentobarbital (50 mg/kg i.p.). The right cremaster muscle was exposed by a ventral incision of the scrotal sac and cleared from connective tissue. The muscle was opened by a ventral incision after which the testis was removed. The cremaster was then excised and pinned to a dissecting dish containing MOPS buffer (composition see below) at 5°C. The first order arteriole was partly dissected and a segment of 1–2 mm length was excised and transferred to a pressure myograph. The myograph consists of a heated chamber, two glass cannulas, a thermistor and was sealed with a glass cover. The chamber and the cannulas were filled with Krebs buffer (composition see below). The arteriole was mounted on both cannulas and secured with sutures. One cannula was connected to a column to pressurize the arteriole and set at 75 mmHg, which is in the in vivo range reported for this arteriole [13]. The other cannula was closed to keep luminal flow zero. The arteriole was superfused with Krebs buffer at 33°C, the in vivo temperature of the cremaster muscle. All drugs were added to the superfusate and not recirculated. A video camera on a microscope was used to visualize the arteriole and an electronic measurement system was used to monitor the inner arteriolar diameter continuously. Segments were equilibrated for 30 min during which a spontaneous tone of about 40–50% reduction in inner diameter developed. At the end of each experiment, 0.1 mM papaverine was added to obtain the maximal diameter.
2.2 Protocol
In the first series, control experiments were done to test the efficacy of NG-nitro-L-arginine (L-NNA), a false precursor for nitric oxide synthesis and indomethacin, an inhibitor of cyclooxygenase. Preliminary experiments showed that 1 µM arachidonic acid induces half maximal dilation. The maximal response to 1 µM arachidonic acid was recorded during spontaneous tone and after addition of 10 µM indomethacin (n=7). In the second group, the effect of L-NNA (0.1 mM) was tested on steady state responses to 0.1 µM acetylcholine and 10 nM Iloprost, a prostacyclin analogue (n=7). Iloprost was used to study the effect of L-NNA on the smooth muscle response to prostaglandins. In the last control group, the endothelium was removed by perfusion of a bolus of 1 ml air through the lumen. Responses to 1 µM arachidonic acid and 0.1 µM acetylcholine were recorded (n=6).
In the second series, the response to 1 µM arachidonic acid was recorded in two or three consecutive conditions in one arteriole. In the first group, responses were obtained during spontaneous tone, after addition of 0.1 mM L-NNA (n=9) to inhibit basal production of nitric oxide and in the presence of a combination of 0.1 mM L-NNA and 3 to 10 nM S-nitroso-N-acetyl-penicillamine (SNAP), a nitric oxide donor (n=7). In the second group, the response to arachidonic acid was recorded in the presence of L-NNA and in the presence of L-NNA and 3 nM nitroprusside, another nitric oxide donor (n=6). In the last group, the response to arachidonic acid was recorded in the presence of L-NNA and in the presence of L-NNA and 10 µM 8-bromoguanosine-3',5'-cyclic monophosphate (8-Br-cGMP; n=6). The concentrations of SNAP and nitroprusside (NP), and 8-Br-cGMP were chosen to compensate the increase in tone induced by L-NNA.
2.3 Statistics
Inner diameter values are reported as mean±s.e.m. in µm. Responses to arachidonic acid, acetylcholine and Iloprost are maximal changes in inner diameters. A paired Student's t-test with Bonferroni correction was used for statistical analysis. Differences were considered significant at the P<0.05 level. When two segments were obtained from one rat, these were not used in the same group of experiments.
2.4 Drugs and solutions
MOPS buffer consisted of (in mM) 145 NaCl, 5 KCl, 2 CaCl2, 1 MgSO4, 1 NaH2PO4, 5 dextrose, 2 pyruvate, 0.02 EDTA and 3,3-(N-morpholino)propanesulphonic acid. Krebs buffer consisted of (in mM) 110 NaCl, 5 KCl, 2.5 CaCl2, 1 MgSO4, 24 NaHCO3, 1 KH2PO4, 0.02 EDTA and 10 dextrose. It was equilibrated with 95% air, 5% CO2 at 33°C, resulting in a pH of 7.4, a pO2 of 150 mmHg and a pCO2 of 35 mmHg, (at 33°C, measured by a blood gas analyzer (ABL-330, Radiometer, Copenhagen). All salts and MOPS were of analytical grades and purchased from Merck, Darmstadt, Germany. Pyruvate, acetylcholine, arachidonic acid, nitroprusside, 8-Br-cGMP and SNAP were obtained from Sigma, St. Louis, USA. L-NNA was from Bachem, Bubendorf, Switzerland. Solutions were prepared fresh daily. Arachidonic acid was kept as a stock solution at –20°C, while aliquots were melted and kept on ice on the day of the experiment. Indomethacin was dissolved in 0.2 M Na2CO3.
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3 Results |
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3.1 Vessel characteristics
A total number of 41 arteriolar segments were studied from 33 rats. All these segments developed spontaneous tone within the equilibration period. Segments that did not develop a stable tone were considered damaged and not further studied. Maximal inner diameters, obtained at the end of each experiment by addition of 0.1 mM papaverine averaged 179±3 µm. Mean inner diameters during spontaneous tone were 98±3 µm for segments with intact endothelium (n=35) and 79±9 µm for endothelium-denuded segments (n=6). Addition of L-NNA (n=28) to endothelium-intact arterioles induced a significant decrease in diameter to 90±3 µm, indicating basal release of nitric oxide. The concentrations of nitric oxide donors SNAP and nitroprusside (NP), and the cGMP analogue 8-Br-cGMP were chosen to compensate the increase in tone induced by L-NNA. Mean diameters are shown in Fig. 1. Addition of indomethacin (n=7) did not affect tone.
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3.2 Efficacy of inhibitors of cyclooxygenase and nitric oxide synthase
Addition of 1 µM arachidonic acid to the superfusate resulted in a transient increase in arteriolar diameter. Typically, maximal dilation was observed around 10 min. after addition of arachidonic acid. After incubation with the cyclooxygenase inhibitor indomethacin responses to arachidonic acid were impaired by 80%. The L-arginine analogue L-NNA inhibited the response to acetylcholine by 63%, but did not significantly affect dilation induced by the prostacyclin analogue Iloprost (P=0.16). After endothelium removal dilatory responses to arachidonic acid and acetylcholine were absent. The results of this series of control experiments are summarized in Table 1.
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3.3 Role of nitric oxide in arachidonic acid metabolism
In the second series of experiments, the role of nitric oxide in the response to arachidonic acid was studied. Fig. 2a shows the results of the first group. The response to arachidonic acid was obtained during spontaneous tone, in the presence of L-NNA and in the presence of L-NNA and SNAP in the same arteriole. Inhibition of endogenous nitric oxide with L-NNA impaired arachidonic acid induced dilation, while the nitric oxide donor SNAP was found to increase dilation. In Fig. 2b, results with the nitric oxide donor nitroprusside are shown. First, the response to arachidonic acid was obtained in the presence of L-NNA. Then, a low concentration of nitroprusside was added, resulting in
15 µm dilation. In this condition, the response to arachidonic acid was significantly increased. In Fig. 2c, results are shown that were obtained with 8-Br-cGMP. Responses to arachidonic acid were obtained in the presence of L-NNA and after addition of 8-Br-cGMP. No effect of 8-Br-cGMP was observed on the response to arachidonic acid.
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4 Discussion |
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TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
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The main finding of the present study is that basal release of nitric oxide augments arachidonic acid induced dilation in arterioles from rat skeletal muscle. Inhibition of the response to arachidonic acid with L-NNA is restored with exogenous nitric oxide donors, SNAP and nitroprusside. Thus, the non-specific inhibitory effect of L-NNA, due to its chemical or structural nature, can be explained by a permissive effect of nitric oxide in arachidonic acid induced dilation.
L-Arginine analogues are known to have non-specific effects. NG-monomethyl-L-arginine (L-NMMA) may stimulate, rather than inhibit nitric oxide synthesis [14]. N-Nitro-L-arginine methylester (L-NAME) and L-NMMA are reported to interact with intracellular iron containing systems [15]. Furthermore, L-NAME and other alkyl esters of arginine are known muscarinic receptor antagonists [16]. Therefore, we used the L-arginine analogue L-NNA in the present study.
In the first series of experiments we found that arachidonic acid induces a transient dilatory response. The response was significantly inhibited by indomethacin, while endothelium-denuded segments showed no dilation. Thus, these results indicate that arachidonic acid induced dilation is mediated by endothelium-derived prostaglandins, in agreement with other reports on isolated arterioles from skeletal muscle [3, 6, 7].
Reports by Koller et al. [8]on cremaster arterioles and by Pratt et al. [9]in bovine coronary arteries show that L-arginine analogues impair arachidonic acid induced dilation. This suggests that arachidonic acid induces the release of nitric oxide. However, as arachidonic acid did not increase the level of the second messenger cGMP in the smooth muscle cells, this possibility is excluded [9]. Thus, it was suggested that L-arginine analogues have other effects than inhibition of nitric oxide.
Our results confirm the inhibitory effect of L-arginine analogues on the response to arachidonic acid, but differ in the interpretation of these results. We found that in the presence of L-NNA, responses were restored with exogenous nitric oxide. Thus, these data demonstrate that arachidonic acid induced dilation is increased by nitric oxide donors. However, the possibility of a non-specific effect of L-NNA on the response to arachidonic acid is not ruled out by these results. Further evidence for our hypothesis can be derived from the study of Koller et al. [8]. In this study, the response to arachidonic acid was also inhibited by another L-arginine analogue, L-NMMA. Thus, inhibition of arachidonic acid induced dilation is not restricted to the L-arginine analogue L-NNA. Furthermore, the response to arachidonic acid was inhibited by L-NNA in a concentration-dependent manner, in a similar concentration range as for the inhibition of acetylcholine-induced release of nitric oxide [8]. It should be mentioned here, that inhibition of the response to acetylcholine by L-NNA is obscured by the contribution of an endothelium-derived hyperpolarizing factor [17]. In the present study, some arterioles did not show an effect of L-NNA (0.1 mM) on spontaneous tone, suggesting the absence of a basal release of nitric oxide. In these arterioles, the change in diameter due to arachidonic acid was not impaired by L-NNA: 51±18 vs. 45±18 µm (n=4). Thus, in these experiments L-NNA was present, but did not affect the response to arachidonic acid. This observation further strengthens our hypothesis that the effect of L-NNA on arachidonic acid metabolism is the result of its biological effect rather than a non-specific effect.
In all other arterioles incubation with L-NNA induced a small increase in tone, indicating basal release of nitric oxide. In the presence of L-NNA, low concentrations of the nitric oxide donors SNAP and nitroprusside were added to compensate the inhibition of endogenous nitric oxide (Fig. 1). Both nitric oxide donors significantly increased the response to arachidonic acid. In contrast, 8-Br-cGMP similarly compensated the increase in tone but did not affect the response to arachidonic acid (Fig. 2). These results suggest a direct effect of nitric oxide on arachidonic acid metabolism. One possibility is that nitric oxide augments the response to prostaglandins at the level of the smooth muscle cells. However, we found no inhibitory effect of L-NNA on dilation induced by the prostacyclin analogue Iloprost (Table 1). If anything, a tendency to an increased response was found. Therefore, it is unlikely that nitric oxide increases smooth muscle sensitivity to prostaglandins, in agreement with other reports [18]. Thus, nitric oxide is most likely to interfere with endothelial prostaglandin synthesis. Since we studied responses to exogenous arachidonic acid, the liberation of arachidonic acid from membrane fatty acids is bypassed. Several studies on cultured endothelial cells have addressed the possibility that nitric oxide modulates cyclooxygenase activity [10–12, 19–21], with conflicting results. No effect of nitrates on prostacyclin synthesis was found in endothelial cells from human umbilical veins or in human vascular fragments [19]. Also, no effect of nitric oxide was found on purified COX-1 [20]. An inhibitory effect of high levels of nitric oxide was observed in bradykinin-induced prostacyclin release in bovine endothelial cells [21]. In this study, the effect is attributed to the second messenger cGMP. On the other hand, an increase in enzymatic activity of cyclooxygenase was found in murine macrophages and human fibroblasts [10]. In bovine aortic endothelial cells, half the shear stress induced prostacyclin release was attributed to nitric oxide-dependent signalling [12]. Furthermore, a detailed study on bovine coronary endothelial cells showed that nitric oxide increases eicosanoid production by stimulating existing cyclooxygenase, independent of cGMP [11]. Thus, the findings of the latter report correspond with our results obtained in the isolated arterioles. The time scale of our experiments favours an effect of nitric oxide on existing cyclooxygenase, rather than de novo synthesis. The mechanism of cyclooxygenase activation may be related to the haem-binding properties of nitric oxide, similar to activation of haem-containing enzymes like guanylate cyclase [11].
An alternative explanation for the observed results may be a change in the type of prostaglandins released. Several reports suggest that in conditions of impaired nitric oxide availability, prostaglandin synthesis may be shifted to constrictor prostanoids. An increase in the formation of the constrictor prostaglandin H2 has been observed in the presence of L-arginine analogues [22]and in arteries of hypertensive rats [2–5]. However, as we did not measure the concentrations of prostanoids directly, further study is needed to substantiate this hypothesis.
In summary, our results show that arachidonic acid induced dilation is modulated by nitric oxide. The effect of nitric oxide may result from a stimulatory effect on cyclooxygenase. The non-specific inhibition by L-arginine analogues may be explained by a permissive effect of basal nitric oxide on arachidonic acid induced dilation.
Time for primary review 21 days.
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References |
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TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
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- Gerritsen ME. Physiological and pathophysiological roles of eicosanoids in the microcirculation. Cardiovasc Res (1996) 32:720–732.
[Abstract/Free Full Text] - Huang A, Koller A. Both nitric oxide and prostaglandin-mediated responses are impaired in skeletal muscle arterioles of hypertensive rats. J Hypertens (1996) 14:887–895.[CrossRef][Web of Science][Medline]
- Huang A, Sun D, Koller A. Endothelial dysfunction augments myogenic arteriolar constriction in hypertension. Hypertension (1993) 22:913–921.
[Abstract/Free Full Text] - Fu-Xiang D, Jameson M, Skopec J, Diederich A, Diederich D. Endothelial dysfunction of resistance arteries of spontaneously hypertensive rats. J Cardiovasc Pharmacol (1992) 20:S190–S192.[Web of Science][Medline]
- Ito T, Kato T, Iwama Y, et al. Prostaglandin H2 as an endothelium-derived contracting factor and its interaction with endothelium-derived nitric oxide. J Hypertens (1991) 9:729–736.[CrossRef][Web of Science][Medline]
- Koller A, Sun D, Kaley G. Role of shear stress and endothelial prostaglandins in flow- and viscosity-induced dilation of arterioles in vitro. Circ Res (1993) 72:1276–1284.
[Abstract/Free Full Text] - Messina EJ, Sun D, Koller A, Wolin MS, Kaley G. Role of endothelium-derived prostaglandins in hypoxia-elicited arteriolar dilation in rat skeletal muscle. Circ Res (1992) 71:790–796.
[Abstract/Free Full Text] - Koller A, Sun D, Messina EJ, Kaley G. L-Arginine analogues blunt prostaglandin-related dilation of arterioles. Am J Physiol (1993) 264:H1194–H1199.[Web of Science][Medline]
- Pratt PF, Rosolowsky M, Campbell WB. Mediators of arachidonic acid induced relaxation of bovine coronary artery. Hypertension (1996) 28:76–82.
[Abstract/Free Full Text] - Salvemini D, Misko T, Masferrer JL, et al. Nitric oxide activates cyclooxygenase enzymes. Proc Natl Acad Sci USA (1993) 90:7240–7244.
[Abstract/Free Full Text] - Davidge ST, Baker PN, McLaughlin MK, Roberts JM. Nitric oxide produced by endothelial cells increases production of eicosanoids through activation of prostaglandin H synthase. Circ Res (1995) 77:274–283.
[Abstract/Free Full Text] - Wang W, Diamond SL. Does elevated nitric oxide production enhance the release of prostacyclin from shear stressed aortic endothelial cells? Biochem Biophys Res Commun (1997) 233:748–751.[CrossRef][Web of Science][Medline]
- Meininger GA, Fehr KL, Yates MB. Anatomic and hemodynamic characteristics of the blood vessels feeding the cremaster skeletal muscle in the rat. Microvasc Res (1987) 33:81–97.[CrossRef][Web of Science][Medline]
- Archer SL, Hampl V. NG-monomethyl-L-arginine causes nitric oxide synthesis in isolated arterial rings: trouble in paradise. Biochem Biophys Res Commun (1992) 188:590–596.[CrossRef][Web of Science][Medline]
- Peterson DA, Peterson DC, Archer S, Weir EK. The non specificity of specific nitric oxide synthase inhibitors. Biochem Biophys Res Commun (1992) 187:797–801.[CrossRef][Web of Science][Medline]
- Buxton ILO, Cheek DJ, Eckman D, et al. NG-nitro L-arginine methyl ester and other alkyl esters of arginine are muscarinic receptor antagonists. Circ Res (1993) 72:387–395.
[Abstract/Free Full Text] - Bakker ENTP, Sipkema P. Components of acetylcholine-induced dilation in isolated rat arterioles. Am J Physiol (1997) 273:H1848–H1853.[Web of Science][Medline]
- Thiemermann C. Biosynthesis and interaction of endothelium-derived vasoactive mediators. Eicosanoids (1991) 4:187–202.[Web of Science][Medline]
- De Caterina R, Dorso CR, Tack-Goldman K, Weksler BB. Nitrates and endothelial prostacyclin production: studies in vitro. Circulation (1985) 71:176–182.
[Abstract/Free Full Text] - Tsai A-L, Wei C, Kulmacz RJ. Interaction between nitric oxide and prostaglandin H synthase. Arch Biochem Biophys (1994) 313:367–372.[CrossRef][Web of Science][Medline]
- Doni MG, Whittle BJR, Palmer RMJ, Moncada S. Actions of nitric oxide on the release of prostacyclin from bovine endothelial cells in culture. Eur J Pharmacol (1988) 151:19–25.[CrossRef][Web of Science][Medline]
- Nakaike R, Shimokawa H, Yasutake H, et al. Effects of L-arginine analogues on vasomotion of isolated porcine coronary arteries. Am J Physiol (1995) 268:H1966–H1972.[Web of Science][Medline]
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